1. Field of the Invention
This invention relates to a suture anchor that allows to connect soft tissues, such as ligaments or tendons, to the bone and, in particular, to mend rotator cuffs and Bankart's lesions.
2. Description of Related Art
In U.S. Pat. No. 5,501,695, in the name of Anspach, is disclosed a two part suture anchor that allows a muscular and tendinous reinsertion into the bone.
This suture anchor includes a first external, cylindrical element attached to the fixation prongs that are separated from each other by means of grooves that are parallel to the longitudinal axis of the suture anchor. The first element houses in its interior a second deformation element that acts in conjuncture with the free element of the fixation prongs
The second deformation element is attached by means of a fracture zone of a dragbar that enables the surgeon, after having introduced the suture anchor into a hole previously drilled into the bone, to slide this second element into the first one in order to axially deform the fixation prongs in the spongy part of the bone.
Since the tension force suffices to deform the fixation prongs, the rod separates from the second element through an irreversible break.
It can be noted that the prongs deform laterally following a direction approximately perpendicular to the longitudinal axis of the suture anchor in order to permanently attach the latter to the inside of the bone.
Lastly, the first element is attached at one of its extremities to a flange that comes to rest against the cortical bone and is provided with a series of holes, used by the surgeon for the attaching of the suture threads.
The above-described suture anchor presents some disadvantages, namely that it is not designed to be removed without causing a complete destruction of the bone or bones to which it is attached. In fact, the anchor is not provided with any means of removal that would allow it to be dislodged from the bone without causing any damage to the bone.
Moreover, beyond the fracture zone of the second element, the suture anchor is not provided with means limiting the displacement of the element in order to prevent the fixation prongs from abnormally breaking under the effects of the tractive force.
Also, U.S. Pat. No. 5,649,963 discloses a suture anchor and an element onto which is screwed a bushing for the attaching of the anchor.
The suture anchor is provided with expansion means that move towards the outside under the pressure of the bushing and the element. It can be noted that the element is provided with a device that allows that the expansion means come together so that they can be removed from the suture anchor.
It can be seen that the suture anchor Is not provided with stop means limiting the deformation of the expansion means when the pressure of the bushing and the element is applied.
U.S. Pat. No. 5,472,452 discloses a suture anchor provided with elastic deformation expansion means and a deformation element guided inside of a hollow body of the anchor to deform the expansion means.
The deformation element presents a specific shape that, being under tractive force, causes the deformation of the elastic expansion means so that they penetrate into the spongy bone, that is near the hole into which was previously introduced the suture anchor.
The deformation element has a specific shape that causes the expansion means be blocked in a position that holds the suture anchor in the spongy bone.
Under the effect of a thrust force, the deformation element penetrates into the suture anchor body to deform anew the expansion means in a direction identical to that of the tractive force.
It can be observed that when the suture anchor is removed, the expansion means penetrate deeper into the spongy bone, entailing the risk that the return of the expansion means to their original position is prevented, which position is obtained due to the elastic characteristics of the expansion means.
GB Patent 2 173 565 discloses a surgical screw constituted by several components that interact to allow the deformation of an expansion means made out of a high-density plastic material.
The surgical screw comprises a hollow, cylindrical body traversed by a threaded element provided with a head, an adjusting nut interacting with the threaded element, and expansion means provided between the cylindrical body and the head of the adjusting nut.
When the threaded element is being turned, the nut penetrates into the hollow body in order to deform the expansion means that are affixed to the head of the nut.
It can be noted that the screw described in patent GB 2 173 565 is not a monobloc, that is to say, that it does not consist of one only piece, and that the expansion means do not have plastic deformation characteristics due to the utilized material.
This invention has the aim to specifically remedy these disadvantages.